Document EP -0,472,219 describes a device for measuring the pressure that prevails in a combustion chamber of an internal-combustion chamber.
This device comprises a seal interposed between the cylinder head of this engine and the engine block, and it is in tight contact with the respective faces of this cylinder head and of this engine block. The seal, of multisheet type, comprises an upper metal sheet and a lower metal sheet between which an intermediate sheet bearing a housing that receives a pressure-sensitive element is arranged.
A pressure inlet bringing the pressure to a measuring surface arranged parallel to the face of the cylinder head or to the face of the engine block is provided to measure the pressure prevailing in the combustion chamber.
This measuring device however has significant drawbacks.
In fact, the pressure inlet can be clogged, or its section at least reduced, by a coke deposit usually generated by combustion. Transfer of the fluid under pressure from the combustion chamber to the measuring surface may therefore be non-existent or greatly disturbed.
Furthermore, it is necessary to either use a seal of great thickness to make the housing intended to receive the sensitive element and the measuring inlet, which requires adjustment of the assembly made up of the cylinder head, the engine block and the piston, or to provide machining work at the level of the cylinder head, thus embrittling it, which may even lead to sealing losses at these machined points or require additional sealing at this level.
Finally, the presence of such a pressure inlet changes the level, the shape, the frequency and the phase of the pressure wave coming from the combustion chamber.
The present invention aims to overcome the aforementioned drawbacks by means of a measuring device of simple design, of relatively low cost and quasi-reliable as regards measurement.